Transient liquid phase bonding of Sn-Pb solder with added Cu particles

Abstract

In this paper, the 1%-20% Cu particles were uniformly distributed in SnPb solder by mechanical mixing method to prepare composite solder. The solder was welded by eutectic welding and the high temperature failure test was carried out. The melting point and internal structure of solder were observed before reflow, after welding and after aging, and the existence of high-temperature resistant skeleton was found. It could be seen from the DSC curve that the solder absorption peak changes in a step-like manner, and the proportion of the high melting point absorption peak gradually increases with the aging process. The micro-structure of solder joints showed that a thin layer of IMC was formed around the Cu particles in the solder joints after welding, and the IMC in the solder joints had grown continuously until they contacted each other and formed a skeleton structure with aging. The skeleton structure improved the high temperature resistance of the solder joint. EDS analysis showed that the distribution of Cu element in the solder was similar to that of Sn, and the Pb element was enriched. The distribution of metal elements indicates that the solder joint was mainly composed of Cu6Sn5 IMC skeleton and Pb rich phase, and the solder component phase was high melting point component transformation.